Mining method and use of mined material in production of graphene and graphitic material

Abstract

A mining method (10) by which graphitic ore is produced in a form that constitutes an appropriate feedstock for an electrolytic process (20) for the production of graphitic materials through exfoliation. The graphitic ore feedstock may be utilised directly as an electrode in the electrolytic process (20). Also disclosed is a graphitic feedstock for an electrolytic process for the production of graphitic material through exfoliation of that feedstock, wherein the feedstock is less than about 99% graphite (w/w) and of a sufficiently cohesive and conductive nature as to allow electrochemical exfoliation therethroughout without fracturing that might result in collapse of a significant portion of the feedstock or that may result in a loss of conductivity throughout a significant portion of the feedstock.

Claims

1. A method for the use of a mined graphite material in the electrolytic production of graphitic material, the method comprising the steps of: 1) mining a graphite ore material using a non-explosive mining method such that the graphite ore material is in a form that constitutes an appropriate feedstock for an electrolytic process for the production of graphitic materials through exfoliation, the mined graphite ore material having an unconfined compressive strength of about 25 to 300 MPa and an electrical resistivity of about 10 Ohm-metre to 0.0001 Ohm-metre; and 2) employing that graphite ore material directly as an electrode in the electrolytic production of graphitic material without significant processing.

2. The method of claim 1, wherein the graphitic materials produced include one or both of graphene and micro-nano graphite.

3. The method of claim 1, wherein the mined graphite ore material has at least one lineal dimension of greater than or equal to about: a. 0.1 metre; or b. 1 metre.

4. The method of claim 1, wherein the mined graphite material is in the form of a quadrilateral solid.

5. The method of claim 1, wherein measures are implemented during transport and handling to reduce any breakage or deterioration of the mined graphite ore material.

6. The method of claim 1, wherein the production of the graphitic material additionally comprises one or more purification steps, the purification steps include one or more of a liquid separation step, a centrifuging step, a chemical leaching step and a thermal purification step.

7. The method of claim 1, wherein the graphite ore material is of a sufficiently cohesive and conductive nature as to allow exfoliation throughout the material during the electrolytic production of graphitic material.

8. The method of claim 1, wherein the graphite ore material has an unconfined compressive strength of about 50 to 200 MPa.

9. The method of claim 1, wherein the graphite ore material is less than about 99% graphite (w/w).

10. The method of claim 1, wherein the graphite ore material comprises gangue materials that is consistently distributed throughout the graphite ore material and are unreactive in the electrolytic process and insoluble in any electrolyte used therein.

11. The mining method of claim 10, wherein the gangue material comprises silicate minerals consistently distributed throughout the graphitic ore material.

12. The mining method of claim 1, wherein the non-explosive mining method is selected from the group consisting of cutting, sawing, splitting, slicing, and combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The present invention will now be described, by way of example only, with reference to several embodiments thereof and the accompanying single drawing, in which:

(2) FIG. 1 is a diagrammatic representation of a method for the use of a mined graphite material in the electrolytic production of graphene in accordance with one embodiment of the present invention.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

(3) The present invention provides a mining method by which graphitic ore, for example graphite ore, is produced in a form that constitutes an appropriate feedstock for a commercially scalable electrolytic process for the production of graphene through exfoliation in which, in one preferred form, the graphite ore feedstock is utilised directly as an electrode in the electrolytic process. It is to be understood that the term graphite ore as it is used herein includes a graphitic ore.

(4) The graphite ore feedstock is extracted from a graphite ore body by non-explosive techniques. The non-explosive technique for extraction of the graphite ore feedstock includes cutting, sawing, splitting and/or slicing (by wire for example).

(5) The graphite ore feedstock is cut, sawn, split or sliced to a size and shape that is able to be used without further size reduction in the electrolytic process for the production of graphene.

(6) The graphite ore feedstock is of a sufficiently cohesive and conductive nature as to allow electrochemical exfoliation therethroughout without fracturing that might result in collapse of a significant portion of the feedstock or that may result in a loss of conductivity throughout a significant portion of the feedstock.

(7) The graphite ore feedstock is appropriately conductive and sufficiently strong to allow its use as an electrode material in the electrolytic process for the production of graphene through exfoliation.

(8) The graphite ore feedstock has an unconfined compressive strength of between about 25 to 300 MPa, more particularly between about 50 to 200 MPa, still more particularly between about 75 to 150 MPa.

(9) The graphite ore feedstock has a resistivity of between about 10 Ohm-metre to 0.00001 Ohm-metre, more particularly from 1 Ohm-metre to 0.0001 Ohm-meter, and still more particularly from 0.1 Ohm-metre to 0.001 Ohm-metre.

(10) The graphite ore feedstock is preferably greater than about 10% graphite (w/w). For example, the graphite ore feedstock comprises more than 10% graphite (w/w), more particularly more than 15% graphite (w/w), and still more particularly above 20% graphite (w/w). Further, the graphite ore feedstock is preferably also less than 99% graphite (w/w), more particularly less than 97% graphite (w/w), and still more preferably less than 95% graphite (w/w).

(11) The graphite ore feedstock further comprises gangue materials that are unreactive in the electrolytic process. The gangue material is also consistently distributed throughout the graphite ore feedstock.

(12) In one form of the present invention the gangue material comprises unreactive and physically strong silicate materials distributed consistently throughout the graphite ore material.

(13) In a still further form of the present invention the graphitic material has a randomly oriented flake morphology.

(14) The present invention further provides a graphitic feedstock for an electrolytic process for the production of graphene through exfoliation of that feedstock, wherein the feedstock is less than about 99% graphite (w/w), for example less than about 95%. The graphitic feedstock is of a sufficiently cohesive and conductive nature as to allow electrolytic exfoliation therethroughout without fracturing that might otherwise result in collapse of a significant portion of the feedstock or that may result in a loss of conductivity throughout a significant portion of the feedstock.

(15) In one form of the present invention the graphitic feedstock is appropriately conductive and sufficiently strong to allow its use as an electrode material in the electrolytic process for the production of graphene through exfoliation.

(16) In one form of the present invention the graphitic feedstock is a graphite ore mined directly from a graphite ore body.

(17) In another form of the present invention the graphitic feedstock is a reconstituted composition. The reconstituted composition comprises a graphitic material and one or more binders. One suitable graphitic material is graphite flake ore.

(18) A reconstituted composition for use in the present invention is such that the binder is sufficiently strong and conductive to allow its use as an electrode material in the electrolytic process for the production of graphene through exfoliation. Alternatively, or in addition to, the graphitic material is arranged within the reconstituted composition such that a current can be passed therethroughout.

(19) Still further provided is a method for the use of a mined graphitic ore material, for example graphite ore, in the electrolytic production of graphene, the method comprising the steps of: 1) Mining a graphitic ore material; and 2) Employing that mined graphitic ore material in the electrolytic production of graphene without significant processing.

(20) The term without significant processing is intended to indicate that the level of processing of the graphite material does not include grinding, fine grinding or micronisation of ground ores, but may include crushing and screening to a size of greater than a P.sub.80 of about 1.18 mm (16 mesh).

(21) If the level of processing employed in the mining of the graphite ore material does employ some level of crushing then the crushed graphite material is reconstituted into an electrode prior to use in the electrolytic production of graphene. The reconstitution of the graphite material comprises the addition of one or more binders, for example hydraulic cement, as noted hereinabove, and which are unreactive with the electrolyte.

(22) The reconstituted graphite ore material composition for use in the present invention is preferably sufficiently strong and conductive to allow its use as an electrode material in the electrolytic process for the production of graphene through exfoliation. Alternatively, or in addition to, the graphitic ore material is arranged within the reconstituted composition such that a current can be passed therethroughout.

(23) The graphitic ore material is used as at least one electrode in the electrolytic production process and, in one form of the present invention, is formed into a shape and size such as to enable a continuous feed of electrode. For example, as one electrode is consumed, another electrode follows that electrode to effectively form a largely uninterrupted flow or continuation of electrode material.

(24) The present invention still further provides a micro-nano graphite having unaltered properties relative to the graphite ore from which it is produced. The micro-nano graphite has an edge morphology unaltered from the graphite ore from which it is produced. It is understood by the Applicants that the micro-nano graphite of the present invention does not exhibit the distortion or rounding of platelet edges that are typically exhibited when graphite materials are exposed to mechanical size reduction processes, for example most milling and comminution processes.

(25) The micro-nano graphite of the present invention may comprise at least about 2% by weight graphene.

(26) The present invention also provides a method for the use of a mined graphite ore material in the production of a graphitic material, the method comprising the steps of: 1) Mining a graphite ore material; and 2) Employing that graphite ore material in the production of a graphitic material without significant processing.

(27) The graphitic material produced by the method immediately above comprises a micro-nano graphite as described above and which in one form comprises at least about 2% by weight graphene. A separation step is employed to separate the micro-nano graphite and the graphene from one another.

(28) In one form of the present invention the production of the graphitic material comprises electrolytic means, again as described hereinabove.

(29) The mined graphite ore material preferably has properties as described hereinabove.

(30) The level of processing of the graphite ore material does not include grinding, fine grinding or micronisation. The level of processing may include coarse crushing to passing size 12 mm and more preferably passing 3 mm. Accordingly, measures are implemented during the transport and handling of the graphite ore material to reduce any breakage or deterioration of the mined graphite.

(31) The production of the graphitic material, being the micro-nano graphite, additionally comprises one or more purification steps. The purification steps include one or more of a liquid separation step, a centrifuging step, a chemical leaching step and a thermal purification step.

Example

(32) The present invention may be further illustrated and understood through reference to the following non-limiting example.

(33) In FIG. 1 there is shown a method 10 for the use of a mined graphite ore material in the electrolytic production of graphene. A suitable graphite ore material, being a strong, conductive graphite bearing ore, has been identified and is available to the Applicant in the Nunasvaara deposit in Sweden, being a predominantly microcrystalline flake Joint Ore Reserves Committee (JORC) mineral resource of 7.6 Mt at 24.4% graphite (Cg). Grades for this deposit have been drill tested at an average of 26.2% Cg, with grades attaining up to 46.7% Cg. The rock strength has been measured at approximately 120 MPa and the resistivity at less than 10 Ohm-meter, for example 0.0567 Ohm-meter.

(34) A deposit of the nature of the Nunasvaara deposit in Sweden would not be, and has not been to date, considered an appropriate source of graphitic material feedstock for prior art processes for the production of graphene, as is set out and discussed in the discussion of the Background Art above.

(35) A raw graphite ore is cut or otherwise extracted from an open pit mine or quarry (not shown) by known bulk mining methods with abrasive disks, saws, splitters or wires and other known non-explosive methods of rock extraction in an ore-extraction step 12. A block size for the raw graphite ore is chosen by an operator so as to be convenient for both removal from the deposit in an electrode handling step 14, and for transport 16 of the ore to the location of a storage facility 18, ideally nearby an electrolytic process plant 20 to which the graphite ore is fed after any necessary additional shaping, cutting or forming 22.

(36) The blocks of ore have sizes which are suitable for transport, transfer movement, and handing. The blocks may be further cut into smaller shapes or forms of electrodes which are considered more suitable for presentation to an electrolytic process.

(37) The blocks of ore have preferred minimum dimension of 50 mm and maximum dimension of 2000 mm. More particularly, the blocks have a minimum dimension of 100 mm and maximum dimension of 1000 mm, or still more particularly a minimum dimension of 150 mm and maximum dimension of 500 mm.

(38) The block shape may be cubic, cylindrical, trapezoidal, conical, or rectangular solid or other shapes which are suitable for transport by trucks or railcars on pallets or other packaging or shipping containers, as well shapes that are particularly suitable for attachment or insertion to any feeding apparatus that may be employed with an electrolytic cell of the electrolytic process 20.

(39) The ore blocks from the graphitic deposit may be employed directly as quarried as electrodes in electrolysis, or further cut into suitable shapes, or have connections inserted or attached that allow electrical current to flow from an external power source into the electrodes at controlled volts and amps.

(40) Each block of quarried graphite ore will be selected to have a combination of carbon grade, i.e. percent graphitic carbon (% Cg), strength (i.e. resistance to fracture or breakage measured in Mega Pascals or MPa by unconfined compressive methods), and electrical resistivity (Ohm-metre).

(41) The ore grade is preferably greater than 10% Cg, for example, more than 15% Cg. One preferred example of ore grade is above 20% Cg.

(42) The ore strength is preferably between about 25 to 300 MPa, for example between about 50 to 200 MPa. One preferred example of ore strength is between about 75 to 150 MPa.

(43) The ore resistivity is preferably between about 10 Ohm-metre to 0.00001 Ohm-metre, for example between about 1 Ohm-metre to 0.0001 Ohm-meter. One preferred example of ore resistivity is between about 0.1 Ohm-metre to 0.001 Ohm-metre.

(44) The ore blocks will also contain gangue, i.e. non-graphitic minerals, which are predominately unreactive in the electrolytic process and insoluble in the electrolyte used in the electrolytic process 20.

(45) The gangue present in the graphite ore is ideally well distributed through the ore and does not occur in veins or layers which would tend to decrease the strength of the blocks during handling or raise resistivity during the electrolytic process 20.

(46) The gangue consists of unreactive and physically strong silicate minerals that are dispersed and spread throughout the ore blocks. The gangue may also preferably consist of small fractions by weight, i.e. less than 12% w/w of sulphide or carbonate or other reactive minerals, for example less than 6% w/w of non-silicate gangue minerals, or more preferably less than 3% w/w of non-silicate gangue minerals.

(47) It is envisaged that any electrolytic process employed in the present invention may comprise electrolytic compositions, electrical currents and voltages (comprising one or more of magnitudes, time-dependent values, and polarity reversals) and/or electrode feed-rates to the electrolytic cell or bath, which optimise the creation of micro-nano graphite and graphene in preference to or in addition to other graphitic materials.

(48) From the above description it can be seen that the mining method and method of use of mined graphite ore material in the electrolytic production of graphene presents significant advantages over those processes of the prior art. The methods of the present invention are unique in that, inter alia, the precursor material that forms the electrode in the cell is, in a preferred form of the present invention, direct from the ground, rather than being a highly purified, processed and expensive natural feedstock or a synthetic feedstock. This provides a significant advantage in terms of reduced capital expenditure compared to prior art processes and competing methods of graphene production. It is envisaged that significant advantages in terms of operational expenditure may also be realised.

(49) It is envisaged that the methods of the present invention for the electrolytic exfoliation of ore, directly as described hereinabove, is able to be achieved at commercial scale, due to the relatively simple and cost effective nature of the steps utilised in combination with the selected character of the graphitic ore.

(50) It is further envisaged that the micro-nano graphite and graphene products of the present invention are capable of being produced in commercial quantities, for example in amounts ranging from 10 kg to tonnes.

(51) Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.